U2AUDIO7-1 on Logitech Z-640 system. It works on 6.1 but the sound output seems not the right channel. But on another PC, Z-640 seems the right output.
The U2AUDIO7-1's Standard Definition Audio Output. (Please neglect the U2AUDIO7-1's Audio Jack's Color.)
1. FRONT - Left/Right
2. SURROUND - Left Surround/Right Surround
3. CENTER/BASS - CENTER(Left Earphone) / BASS (Right Earphone)
4. BACK - Left/Right (Only at 7.1 mode)
STEP 1 - Make Settings on U2AUDIO7-1's Setting Panel.
The Logitech Z-640 is a 6-channel Audio Speaker System, so let's set the U2AUDIO7-1's Audio output to 6-channel.
STEP 2 -Test the Audio Output Channel
Just use a standard 3.5mm audio Earphone (3-section 3.5mm audio jacks).
2.1 - Connect the earphone's 3.5mm audio jack to the audio ports:
2.1.1 - FRONT (2CH, 4CH, 6CH Speaker Mode)
2.1.2 - SURROUND (4CH, 6CH, 8CH Speaker Mode)
2.1.3 - CENTER/BASS (6CH, 8CH Speaker Mode)
2.1.4 - BACK (Only 8CH Speaker Mode) *
Test Result - If all of the sound output signals from U2AUDIO7-1 are all right, then the U2AUDIO7-1 functions normal. Please check the Logitech Z-640's Speaker Connection.
STEP 3 - Check Logitech Z-640's Speaker's Connection if you are willing.
From the Logitech Z-640's manual, it has Green, Black and Orange Plugs to make a 6.1 output connection. Once we confirm STEP 2 is alright, we suggest you adjust the connection of the speakers.